Specific Defenses of the Host: The Immune Response

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1

Immunity

A specific, defensive response to an invasion by foregone organisms

2

Nonspecific (innate) immunity

Built-in resistance

3

Acquired Immunity

Developed during lifetime

4

Antigen (Ag)

Substance that stimulates production of antibodies (Ab)

5

Naturally Acquired Immunity

Actively sick, results from an infection

6

Naturally Acquired Passive Immunity

Transplacental or via colostrum (give Ab to baby)

7

Artificially acquired active immunity

Vaccination, injection of Ag

8

Artificially acquired passive immunity

Injection of Ab

9

Anti-serum

Serum containing Ab, gives immediate protection but short lived, 2-3 weeks

10

Humoral immunity

  • Involves Ab produced by B cells, found in extracellular fluids
  • Uses Ab in response to Ag
11

Cell-Mediated Immunity

  • Directly utilizes specialized lymphocytes
  • T-lymph do not produce Ab, rather they have receptors that allow T-cells to recognize many kinds of Ag
12

Structure of Ab

  • Immunoglobins
  • 2 or more Ag-binding sites (valences)
  • Bivalent - monomer
  • Two heavy and two light chains
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Types of Ab

  • IgG
  • IgM
  • IgE
  • IgD
  • IgA
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IgG Ab

  • 80% of serum Ab
  • Blood, lymph and intestine
  • Can cross placenta
  • Mainly in second exposure and long lived
15

IgM Ab

  • 5%-10%
  • First on scene
  • Made in initial exposure then decline rapidly
  • Remains in BV
  • Usually Ab against blood type
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IgA Ab

  • 10%-15%
  • In secretions
  • Stop pathogen from attaching to mucous sufrace
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IgD Ab

  • 0.2% of serum Ab in blood, lymph and on B cells
  • Antigen receptors on B cells
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IgE Ab

  • 0.002% of serum Ab
  • On mast cells and basophils
  • Cause mast cell to release histamines
  • Allergic rxn & lysis of parasitic worms
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Clonal Selection

  • Bone marrow gives rise to B cells
  • Mature B cells migrate to lymphoid organs
  • Recognize epitopes
  • B-cells produce plasma cells which produce Ab and memory cells
20

Clonal Deletion

Process of destroying B and T cells that react to self-Ag

21

Ag-Ab complex

  • Ag bound to Ab
  • Some B cells become cancerous & grow rapidly
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Immunological Memory

  • Primary response: slow rise in Ab tier
  • Secondary response: memory cells quickly divide into plasma cells which produce Ab
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Immune System Communication

  • Cytokine: chem messenger within immune system
  • Interleukin: communication between leukocytes
  • Chemokine: cause leukocyte to move to an infection
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Types of T cells

  • Helper T Cell
  • Cytotoxic T Cell (most lethal)
  • Delayed Hypersensitivity
  • Suppressor T Cell
  • Natural Killer Cell
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Helper T Cell

  • Th1: Activate cells related to cell-mediated immunity
  • Th2: Activate B cells to produce eosinophils, IgM and IgE
26

Cytotoxic T Cell

  • Mainly against impaired host cell
  • Cancer cells
  • Tissue transplant
  • Viral infection
  • Intracellular bacteria
  • Destroy target cell with perforin
27

Delayed Hypersensitivity Cell

Associated with allergic reaction, transplant rejection, tuberculin skin test

28

Suppressor T Cell

Turn off immune response when Ag no longer present

29

Natural Killer Cell

  • Lymphocytes that destroy other cells
  • Not specific, attack any cell covered with an Ab
30

Ab-Dependent Cell-Mediated Cytotoxicity

  • Organisms too large for phagocytosis
  • First coated w/ Ab
  • NK cells, macrophages, eosinophils and neutrophils bind to Ab
  • Cells secrete substances to attack organism